Association information received from a number of mobile devices is recorded at a server end, where each mobile device is associated with a user that is pre-registered with the server end. An identification request is received at the server end and from a cashier device, where the identification request includes identity information associated with a particular user. One or more payment candidates corresponding to the cashier device are determined by the server end. A particular user account corresponding to the particular user is determined by the server end by comparing the identity information from the identification request with identity information associated with each of the payment candidates. The particular user account is returned by the server end to the cashier device for making a payment.